Time synchronization of mobile channel sounding system

ABSTRACT

In one example, a processing system of a mobile channel sounding transmitter including at least one processor may establish a wireless side link between the mobile channel sounding transmitter and a channel sounding receiver, transmit, to the channel sounding receiver, a wireless synchronization signal via the wireless side link, and transmit at least one channel sounding waveform in accordance with the wireless synchronization signal. In another example, a processing system of a channel sounding receiver including at least one processor may establish a wireless side link between a mobile channel sounding transmitter and the channel sounding receiver, obtain, from the mobile channel sounding transmitter, a wireless synchronization signal via the wireless side link, and obtain, from the mobile channel sounding transmitter, at least one channel sounding waveform in accordance with the wireless synchronization signal.

This application is a continuation of U.S. patent application Ser. No.16/527,180, filed Jul. 31, 2019, now U.S. Pat. No. 11,082,265, which isherein incorporated by reference in its entirety.

The present disclosure relates generally to wireless communicationnetworks, and more particularly to methods, non-transitory computerreadable media, and apparatuses for synchronizing a mobile channelsounding transmitter and a channel sounding receiver via a wireless sidelink.

BACKGROUND

A wireless channel sounder is a device for measuring wireless channelrelated parameters such as complex impulse response, path loss, receivedsignal strength (RSS), excess delay, or root-mean-square (RMS) delayspread, Doppler spread, fade rate, angle of arrival (AoA) and/or angleof departure (AoD), and the like, as experienced by a user equipment orbase station. In one implementation, a wireless channel sounder mayutilize a directional antenna. For instance, to measure AoA using adirectional antenna, the antenna may be turned in incremental steps tomeasure the RSS. The AoA is recorded where the RSS is at a maximum.While this solution is inexpensive, it is a relatively slow measurementtechnique.

SUMMARY

In one example, the present disclosure discloses a method,computer-readable medium, and mobile channel sounding transmitter forsynchronizing a mobile channel sounding transmitter and a channelsounding receiver via a wireless side link. For example, a processingsystem of a mobile channel sounding transmitter including at least oneprocessor may establish a wireless side link between the mobile channelsounding transmitter and a channel sounding receiver, transmit, to thechannel sounding receiver, a wireless synchronization signal via thewireless side link, and transmit at least one channel sounding waveformin accordance with the wireless synchronization signal.

In another example, the present disclosure discloses an additionalmethod, computer-readable medium, and mobile channel sounding receiverfor synchronizing a mobile channel sounding transmitter and a channelsounding receiver via a wireless side link. For instance, a processingsystem of a channel sounding receiver including at least one processormay establish a wireless side link between a mobile channel soundingtransmitter and the channel sounding receiver, obtain, from the mobilechannel sounding transmitter, a wireless synchronization signal via thewireless side link, and obtain, from the mobile channel soundingtransmitter, at least one channel sounding waveform in accordance withthe wireless synchronization signal.

BRIEF DESCRIPTION OF THE DRAWINGS

The teachings of the present disclosure can be readily understood byconsidering the following detailed description in conjunction with theaccompanying drawings, in which:

FIG. 1 illustrates an example system, in accordance with the presentdisclosure;

FIG. 2 illustrates an example translation of spatial orientationinformation of a local coordinate system with respect to a mobileendpoint device into spatial orientation information in a globalcoordinate system, in accordance with the present disclosure;

FIG. 3 illustrates a flowchart of an example method for synchronizing amobile channel sounding transmitter and a channel sounding receiver viaa wireless side link;

FIG. 4 illustrates a flowchart of an additional example method forsynchronizing a mobile channel sounding transmitter and a channelsounding receiver via a wireless side link; and

FIG. 5 illustrates an example of a computing device, or computingsystem, specifically programmed to perform the steps, functions, blocks,and/or operations described herein.

To facilitate understanding, similar reference numerals have been used,where possible, to designate elements that are common to the figures.

DETAILED DESCRIPTION

The present disclosure broadly discloses methods, computer-readablemedia, and devices for synchronizing a mobile channel soundingtransmitter and a channel sounding receiver via a wireless side link.Developing 3GPP Fifth Generation (5G) standards include the use ofmillimeter wave frequencies (30 GHz to 300 GHz) as carrier frequencies.The propagation loss of air at such frequencies is relatively high. Onetechnique to overcome this loss is the use of beamformed wirelesscommunication. In beamformed communications, wireless signals aretransmitted in a narrow beam. The concentration of energy in a narrowbeam helps overcome the propagation loss of the wireless medium.Similarly, 5G receivers may also sense wireless signals in a narrowregion of space, allowing the capture of a large amount of signal energyand correspondingly low amounts of noise and interference energy. Thisis relevant to channel sounding, as 5G channel models should providemetrics with respect to a spatial grid around the transmitter or thereceiver.

For deployment and configuration of wireless network infrastructure, itis beneficial to obtain a wireless channel's propagation within thefrequency bands of interest to the standard. The act of making suchwireless channel propagation measurements is known as channel sounding.Channel sounding typically operates by transmitting a known wirelesssignal in the frequency band of interest by a channel soundingtransmitter, and subsequently receiving this signal at a differentlocation by a channel sounding receiver. Knowing both the transmittedand the received signal, the state of the channel at the time oftransmission can be extracted, resulting in what may be referred to as a“channel snapshot.” Multiple of such channel snapshots can be acquiredby varying the hardware location, orientation, speed, time oftransmission, and even the environment around the channel soundertransmitter and the channel sounding receiver. The resulting dataset ofchannel snapshots may be subsequently analyzed to extract channel modelsto be used for standards development, as well as network infrastructuredeployment, configuration, and optimization.

Based on multiple antennas at both transmitters and receivers, a M×N (Mtransmit antennas and N receive antennas) multiple input multiple output(MIMO) channel sounding system is able to measure directional channelpropagation at both ends of the wireless link (e.g., at the transmit andreceive antennas) and improve resolution of the spatial multiple pathparameters. In one example, a channel sounding system may transmit aknown signal (broadly a “channel sounding signal” or “channel soundingwaveform”) via a first transmit beam direction of a channel soundingtransmitter, and measure the channel parameters via all N receiveantennas at the channel sounding receiver. The channel soundingtransmitter may then switch to a second transmit beam direction and theprocess repeats until all M×N combinations have been performed.

To enable accurate channel sounding, the channel sounding transmitterand channel sounding receiver should be synchronized. In a current MIMOchannel sounding system, a channel sounding receiver may require apre-allocated measurement time before the channel sounding transmittercan switch from one beam direction to another and/or from one locationto another. Thus, for a receiver to perform all measurements, dataprocessing, and so on, the receiver may require information on whichtransmit beam is currently being used, as well as a means to inform thetransmitter to switch to the next beam direction and/or position. Incertain channel sounding systems, for fully clocksynchronization/recovery the control link has been either over afiber/cable link where the length of cable is known, or using a rubidiumclock which may still drift after an hour or so. The former ischallenging for outdoor measurements due to the impracticality of havinga cable/fiber deployed over the measurement area and the latter mayrequire resynchronization at least every hour.

Examples of the present disclosure describe methods, computer-readablemedia, and devices for synchronizing a mobile channel soundingtransmitter and a channel sounding receiver via a wireless side link. Inparticular, the wireless side link may be a wireless connection thatutilizes different resources from the channel sounding. For instance,the wireless side link may comprise an out-of-band wireless link, suchas a cellular or non-cellular wireless communication session (e.g., anLTE-based or IEEE 802.11/Wi-Fi-based communication session), where thechannel sounding takes place on a different set of time and frequencyresources than used by the wireless communication session. In oneexample, the out-of-band wireless link may comprise a communicationsession between the mobile channel sounding transmitter and the channelsounding receiver in accordance with a set of non-restricted frequencyresources (e.g., in one or more Industrial, Scientific, and Medical(ISM) radio band(s), such as 915 MHz, 2.4 GHz, or 5GHz). Similar to theprevious examples, the channel sounding takes place on a different setof time and frequency resources than used by the wireless communicationsession. In addition, the transmitter and receiver may establish thecommunication session over the non-restricted frequency resources over aproprietary non-standardized PHY and/or via a software defined radio(SDR).

In another example, the out-of-band wireless link may comprise acommunication session between the mobile channel sounding transmitterand the channel sounding receiver using frequency resources that arewithin an operational bandwidth of the transceivers at the transmitterand the receiver that are used for channel sounding, but outside of thefrequencies within the operational bandwidth that are used for thechannel sounding signals, or waveforms. In still another example, thewireless side link may comprise an in-band wireless link which uses thesame frequency resources as are used for the channel soundingwaveform(s), but which utilizes different, non-overlapping time slotsfrom the channel sounding waveforms. Although examples of the presentdisclosure are applicable to a wide range of frequency bands, in oneexample, the present disclosure may relate to channel sounding incentimeter and millimeter wave ranges. For instance, for all of theexamples herein, the considered wireless cellular communicationsstandard may be the Third Generation Project (3GPP) New Radio (NR)and/or 5G radio access technology.

The wireless side link may be used to transmit a synchronization signalconveying clock timing information of the mobile channel soundingtransmitter to the channel sounding receiver. In one example, thesynchronization signal may further convey information regarding one ormore channel sounding waveforms to be transmitted from the mobilechannel sounding transmitter. For instance, the information regardingthe at least one channel sounding waveform may include a transmit beamidentifier, one or more modulation parameters of the at least onechannel sounding waveform, and so forth. By way of example and withoutany limitation, a Zadoff-Chu (ZC) sequence in the time domain may beused for channel sounding. In another example, in the case of frequencydomain processing, the sounding signal may be inserted before an inverseFast Fourier Transform (iFFT) stage in the transmitter. Thus, parametersmay include an identification of a modulation coding scheme e.g., abinary phase shift keying (BPSK) modulation coding scheme, a quadraturephase shift keying (QPSK) modulation coding scheme, a frequencymodulation (FM) scheme, an amplitude modulation (AM) scheme, a frequencyshift keying (FSK) scheme, a modulation coding scheme based upon aprecoding matrix indicator, or a modulation coding scheme based uponprecoder cycling. Higher level encoding schemes such as 16-QAM, 64-QAM,and the like may also be used in other examples.

In one example, the synchronization signal is modulated to include theinformation regarding the at least one channel sounding waveform. Toillustrate, RF signals may be transmitted in a frequency or range offrequencies and extend for a certain duration of time and may have acertain RF energy. A drop of the transmission of the RF signals by themobile channel sounding transmitter (e.g., a drop in the RF energy, suchas to zero) may then be used as a timing indicator for the channelsounding receiver. However, the RF signals may be further modulated toinclude the information regarding an intended transmission of one ormore channel sounding waveforms, e.g., the beam identifier, thecharacteristics of the channel sounding waveform, etc. Other types ofmodulation may be used such that the synchronization signal itself mayinclude the additional information regarding the channel soundingwaveform. In other words, the additional information may be embedded inthe synchronization signal.

As mentioned above, the wireless side link may comprise an out-of-bandwireless link, such as a cellular or non-cellular wireless communicationsession (e.g., an LTE-based or IEEE 802.11/Wi-Fi-based communicationsession), a communication session via non-restricted frequency resources(e.g., in ISM band(s)), or via frequency resources that arenon-overlapping with frequency resources that are utilized for theactual channel sounding. In these examples, the synchronization signal(and additional information regarding one or more channel soundingwaveforms) may alternatively or additionally be conveyed in data packetsor other protocol data units (PDUs) (e.g., IP packets, TCP datagrams,Ethernet frames, Ethernet packets, etc., all of which may broadly bereferred to herein as “packets” or PDUs) according to one or morecommunication protocols utilized for the communication session. Forexample, an LTE-based wireless communication session between a mobilechannel sounding transmitter and channel sounding receiver may traverseat least one base station and other infrastructures of a cellularnetwork. In such case, the mobile channel sounding transmitter andchannel sounding receiver may measure network latency and may utilizethe network latency to calculate an offset based upon the timinginformation of the synchronization signal.

In one example, the present disclosure may comprise mobile channelsounding transmitters and/or receivers that include multiple phasedarray antennas, e.g., where radio frequency (RF) components, such aspower amplifiers, variable phase shifters, and transceivers that areintegrated with the antennas elements of each phased array. Inparticular, examples of the present disclosure may provide a channelsounding system that may operate in one or more frequency bands for 5Gcommunications, and which may determine measurements of wireless channelparameters (e.g., one or more “key performance indicators” (KPIs)), suchas a complex impulse response, a path loss, a received signal strength(RSS), e.g., a reference signal received power (RSRP), acarrier-to-interference (CIR) ratio (or signal-to-noise ratio (SNR)), anexcess delay, a root-mean-square (RMS) delay spread, an angular spread,a Doppler spread, a fade rate, an angle of arrival (AoA), and the like,along with spatial orientation information, such as azimuth andelevation angles, and locations associated with the measurements.

The channel sounding receiver may comprise a device that is equipped tooperate according to the specification of the considered wirelesscellular communications standard (e.g., 5G millimeter wave multiple-inmultiple-out (MIMO)). In one example, the channel sounding receiver mayinclude at least three phased array antennas arranged to provide areceive beam coverage across 360 degrees in azimuth, and may beconfigured with the ability to simultaneously beam sweep multiplereceive beams for the respective phased array antennas to receivechannel sounding waveforms from the mobile channel sounding transmitterand to determine measurements of wireless channel parameters based uponthe channel sounding waveforms that are received. In other words, the atleast three phased array antennas provide receive beams that aresteerable so that for each azimuthal direction, at least one receivebeam is steerable to include the azimuthal direction within thehalf-power beam width angular coverage of the at least one receive beam.

Antenna array geometry defines the placement of the antenna elements onthe phased array antenna. For example, a uniform rectangular array (URA)geometry has antenna elements placed in a rectangular pattern with equalspacing between neighboring elements. Planar geometries such as the URAtypically have a spatial region within which they can transmit orreceive via a narrow beam (e.g., a half power beam width (HPBW) of lessthan 30 degrees angular spread, less than 15 degrees angular spread,less than 10 degrees angular spread, and so forth). In order to coverthe entire 360 degree field of view in the azimuth plane around thereceiver device, multiple planar phased array antennas may be arrangedside-by-side. For instance, in one example, three planar phased arrayantennas may be arranged in a generally triangular layout. In anotherexample, four planar phased array antennas may be arranged in agenerally square or rectangular layout with each phased array antennacovering at least 90 degrees in azimuth. In such case, if the azimuthspatial coverage of each phased array antenna is greater than or equalto 90 degrees, the four phased array antennas can combine to cover all360 degrees. Similarly, a configuration of three phased array antennasmay cover the entire azimuth field of view as long as each phased arrayantenna has greater than or equal to 120 degrees of coverage. In anotherexample, the present disclosure may utilize a cylindrical phased arrayantenna, with antenna elements placed either uniformly or non-uniformlyon the face of the array. A complete cylinder with antenna elements onthe surface can provide 360 degrees of azimuthal coverage. In anotherexample, two half-cylinder phased array antennas can also providesimilar coverage.

It should be noted that in various examples, the phased array antennasmay have different fields-of-view in an elevation plane. For example,the phased array antennas may have a field of view in elevation of 120degrees, 90 degrees, 60 degrees etc. The elevation field of view may besymmetric around the horizon (or a horizontal plane with respect to adevice chassis) or may be offset, e.g., to provide greater coverageabove or below a horizontal plane. For instance, the top edges of thephased array antennas may be angled towards each other, while the bottomedges of the phased array antennas may be angled away from each other.In another example, multiple phased array antennas may be arranged toprovide 180 degrees of elevation coverage.

Appropriate control circuitry may also be paired with the phased arrayantennas. For example, if there are N phased array antennas, there maybe N independent receive beams that can be utilized simultaneously. Inone example, the receiver device may include N radio frequency (RF)front ends (including, for example: variable phase shifters, poweramplifiers, diplexers or switches, downconverters, and the like) and Ndigital baseband units (which may include transceivers) to sense thesignals received via the respective N phased array antennassimultaneously. A receiver device with the ability to capture N beams atthe same time can sweep through the 360 degree field of view quickly bydividing the total azimuth field of view into N smaller coverage zonesfor each of the receive beams of the N phased array antennas.

In one example, the N signals coming out of the N phased array antennascan be fed into a single baseband receiver via a switch (or bank ofswitches). The switch(es) may be used to select one beam at any giventime. In such an example, the receiver device may sweep the beamsthrough their respective fields of view in a sequential manner,resulting in a slower sweep of the 360 degree field of view. By placingadditional switches and baseband receivers, the number of basebandreceivers can be set anywhere between 1 to N, in order to achieve adesired balance of cost, device size, performance speed, etc. In anotherexample, each phased array antenna may be provided with its owndedicated RF front end.

It should be noted the mobile channel sounding transmitter may besimilarly equipped with M phased arrays, M RF front ends, and 1-Mdigital baseband units. The mobile channel sounding transmitter andchannel sounding receiver may each be equipped with analog-to-digitalconverters (ADCs) and digital-to-analog converters (DACs) (e.g., in thebaseband units) which may define the operational range for channelsounding.

In accordance with the present disclosure, a channel sounding receivermay tag a wireless channel parameter measurement withdirectional/spatial orientation information, i.e., in addition to alocation. In one example, the channel sounding receiver may calculate adirection, or spatial orientation of a receive beam with respect to alocal coordinate system, e.g., a three dimensional space withdimensions/axis aligned to a length, a width, and a depth of thereceiver device, for example. In yet another example, the channelsounding receiver may associate the angle of arrival (AoA) with awireless channel parameter measurement (and a location), (e.g., wherethe wireless channel parameter measurement relates to a received power).In one example, the channel sounding receiver does not tag a wirelesschannel parameter measurement (e.g., received signal strength) withspatial orientation information, but rather tags spatial orientationinformation of a measurement with the location. For instance, at a givenlocation, the primary direction from which the signal energy arrives isrecorded, but not the actual received signal strength.

In one example, locations, or geographic positions may be determined atthe channel sounding receiver device via a Global Positioning System(GPS) receiver, or may be derived using other location estimationmethods, such as cell identifier (cell ID) based methods, observed timedifference of arrival (OTDA) techniques, or barycentric triangulation.In this regard, it should be noted that any references herein to achannel sounding receiver may comprise a mobile channel soundingreceiver, i.e., a device that is portable and which can be moved fromlocation to location. For instance, a mobile channel sounding receivermay be moved with relative ease, such as one that may be carried by aperson or wheeled on a small cart that may be pushed or pulled by aperson. In addition, the orientation of the channel sounding receivermay be determined from a gyroscope and compass, allowing the channelsounding receiver device to determine a receive beam direction/spatialorientation, and to therefore measure wireless channel parameters withhigh spatial accuracy.

In should also be noted that in some examples (e.g., for examples wherethe synchronization signal is conveyed wirelessly between the mobilechannel sounding transmitter and the channel sounding receiver withouttraversing any other network infrastructures, or peer-to-peer) thelocation of the channel sounding receiver may also be used by the mobilechannel sounding transmitter to transmit the synchronizations signal. Toillustrate, the channel sounding receiver may report its location to themobile channel sounding transmitter. In one example, the channelsounding receiver may report the location via the wireless side link.For instance, the wireless side link may comprise an in-band orout-of-band wireless link for establishing a bidirectional communicationsession between the mobile channel sounding transmitter and the channelsounding receiver. Thus, the wireless side link may convey asynchronization signal (and in one example, information regarding thechannel sounding waveform) in addition to conveying location informationand other communications between the channel sounding receiver to themobile channel sounding transmitter.

In addition, the mobile channel sounding transmitter may determine itsown location in the same or a similar manner as the channel soundingreceiver and may calculate a direction (and in one example, a distance)between the mobile channel sounding transmitter and the channel soundingreceiver. The mobile channel sounding transmitter may then send thesynchronization signal using one or more phased arrays in the directionof the channel sounding receiver. The mobile channel soundingtransmitter may transmit with a relatively focused beam, e.g., with aHPBW of 15 degrees or less, or with a broader beam e.g., up to 60 to 90degrees of HPBW centered on the direction of the channel soundingreceiver, up to 120 degrees, etc.

It should also be noted that in one example, the wireless side link maybe used to coordinate between the channel sounding receiver and themobile channel sounding transmitter. For instance, the channel soundingreceiver may use the wireless side link to communicate to the mobilechannel sounding transmitter that the channel sounding receiver isdeployed in a location and ready to receive channel sounding waveformsand measure wireless channel parameters. The mobile channel soundingtransmitter may then transmit one or more synchronization signals. Inone example, the channel sounding receiver may transmit a confirmationthat it has received the synchronization signal and is synchronized withthe transmitter before the transmitter begins sending the channelsounding waveform(s). Similarly, if the channel sounding receiver ismeasuring over multiple receive beam directions for multiple transmitbeam directions, the channel sounding receiver may signal to the mobilechannel sounding transmitter that measurements for a sequence of beamsis completed. In addition, if the channel sounding receiver is not ableto obtain certain measurements, e.g., for reasons other than poorwireless channel conditions (such as due to a processing problemon-board the channel sounding receiver, a physical disturbance (e.g., atechnician bumping into the channel sounding receiver), etc.), thechannel sounding receiver may signal to the mobile channel soundingtransmitter over the wireless side link to request a resynchronization.For instance, the mobile channel sounding transmitter may send one ormore synchronization signals, in one example the channel soundingreceiver may confirm synchronization to the synchronization signal, themobile channel sounding transmitter may retransmit one or more channelsounding waveforms for which the measurements were not previouslyobtained, and so on.

In one example, the channel sounding receiver may store one or morewireless channel parameter measurements in a record, along with thespatial orientation information and a location associated with thewireless channel parameter measurements, e.g., in a local memory. In oneexample, the channel sounding receiver may be deployed to obtainwireless channel parameter measurements at various locations within anenvironment and may collect and store all of the measurements. Themeasurements may then be retrieved at a later time and transferred toanother device or system for storage and/or analysis. For instance,similar data from the mobile channel sounding transmitter regarding thetransmit beam(s), the channel sounding waveforms, the location(s) of themobile channel sounding transmitter, etc. may be uploaded to the samedevice or system and correlated with the measurements of the channelsounding receiver. In another example, the measurements from the channelsounding receiver may be transferred to the mobile channel soundingtransmitter for storage and/or analysis. This can be done afterobtaining a series of measurements, e.g., via a cable connection whenthe mobile channel sounding transmitter and receiver are together in asame location. However, in another example, all or a portion of thewireless channel parameter measurements may be transmitted wirelessly bythe channel sounding receiver to the mobile channel sounding transmittervia the wireless side link. In one example, the channel soundingreceiver may indicate to the mobile channel sounding transmitter that ithas one or more records of wireless channel parameter measurements readyfor transmission and the mobile channel sounding transmitter may confirmthat it is ready to receive the measurements. For example, the channelsounding receiver may allocate a limited amount of memory and/or storagefor the records of wireless channel parameter measurements. Accordingly,in one example the receiver device may indicate to the mobile channelsounding transmitter to transfer the record(s) of wireless channelparameter measurements before the allocated memory and/or storagecapacity is reached. It should be noted that all of these communicationsmay occur between the mobile channel sounding transmitter and thechannel sounding receiver via the wireless side link. These and otheraspects of the present disclosure are discussed in greater detail belowin connection with the examples of FIGS. 1-5.

To better understand the present disclosure, FIG. 1 illustrates anexample network, or system 100 in which examples of the presentdisclosure for synchronizing a mobile channel sounding transmitter and achannel sounding receiver via a wireless side link may operate. In oneexample, the system 100 includes a telecommunication service providernetwork 170. The telecommunication service provider network 170 maycomprise a cellular network 101 (e.g., a 4G/Long Term Evolution (LTE)network, a 4G/5G hybrid network, or the like), a service network 140,and a core network, e.g., an IP Multimedia Subsystem (IMS) core network115. The system 100 may further include other networks 180 connected tothe telecommunication service provider network 170. FIG. 1 alsoillustrates various mobile endpoint devices, e.g., user equipment (UE)116 and 117. The UE 116 and 117 may each comprise a cellular telephone,a smartphone, a tablet computing device, a laptop computer, a pair ofcomputing glasses, a wireless enabled wristwatch, or any othercellular-capable mobile telephony and computing devices (broadly, “amobile endpoint device”).

In one example, the cellular network 101 comprises an access network 103and a core network, Evolved Packet Core (EPC) network 105. In oneexample, the access network 103 comprises a cloud RAN. For instance, acloud RAN is part of the 3^(rd) Generation Partnership Project (3GPP) 5Gspecifications for mobile networks. As part of the migration of cellularnetworks towards 5G, a cloud RAN may be coupled to an EPC network untilnew cellular core networks are deployed in accordance with 5Gspecifications. In one example, access network 103 may include cellsites 111 and 112 and a baseband unit (BBU) pool 114. In a cloud RAN,radio frequency (RF) components, referred to as remote radio heads(RRHs), may be deployed remotely from baseband units, e.g., atop cellsite masts, buildings, and so forth. In one example, the BBU pool 114may be located at distances as far as 20-80 kilometers or more away fromthe antennas/remote radio heads of cell sites 111 and 112 that areserviced by the BBU pool 114. It should also be noted in accordance withefforts to migrate to 5G networks, cell sites may be deployed with newantenna and radio infrastructures such as multiple input multiple output(MIMO) antennas, and millimeter wave antennas. In this regard, a cell,e.g., the footprint or coverage area of a cell site, may in someinstances be smaller than the coverage provided by NodeBs or eNodeBs of3G-4G RAN infrastructure. For example, the coverage of a cell siteutilizing one or more millimeter wave antennas may be 1000 feet or less.

Although cloud RAN infrastructure may include distributed RRHs andcentralized baseband units, a heterogeneous network may include cellsites where RRH and BBU components remain co-located at the cell site.For instance, cell site 113 may include RRH and BBU components. Thus,cell site 113 may comprise a self-contained “base station.” With regardto cell sites 111 and 112, the “base stations” may comprise RRHs at cellsites 111 and 112 coupled with respective baseband units of BBU pool114. In accordance with the present disclosure, any one or more of cellsites 111-113 may be deployed with antenna and radio infrastructures,including multiple input multiple output (MIMO) and millimeter waveantennas. In one example, any one or more of cell sites 111-113 maycomprise one or more directional antennas (e.g., capable of providing ahalf-power azimuthal beamwidth of 60 degrees or less, 30 degrees orless, 15 degrees or less, etc.). In one example, any one or more of cellsites 111-113 may comprise a 5G “new radio” (NR) base station.

In one example, the channel sounding receiver 120 and the channelsounding transmitter 125 (e.g., a mobile channel sounding transmitter)may be used to determine a plurality of measurements of at least onewireless channel parameter (broadly, “channel sounding”). In oneexample, channel sounding receiver 120 may comprise a user equipment,e.g., a mobile endpoint device comprising a cellular telephone, asmartphone, a tablet computing device, a laptop computer, or any othercellular-capable mobile telephony and computing devices.

In one example, channel sounding receiver 120 may comprise a dedicatedchannel sounding device. Similarly, the channel sounding transmitter 125may comprise a dedicated channel sounding device.

In one example, the channel sounding transmitter 125 may comprise aswitched antenna array with transmitting antennas having differentorientations, e.g., a curved array. For instance, in one example, aswitched antenna array to transmit wireless test signals may have seventransmitting antennas, each antenna oriented to cover 18.5 degrees ofazimuth at half-power beamwidth, which may cover a total of 120 degreesin azimuth (with a small overlap in beamwidth for adjacent antennas inthe array). In one example, the channel sounding transmitter 125 maycomprise one or more phased antenna arrays (e.g., a quantity of M phasedarrays), M RF front ends, and 1-M digital baseband units. In oneexample, the channel sounding transmitter 125 may transmit channelsounding signals (also referred to as “channel sounding waveforms”) forreception and measurement of wireless channel parameters by the channelsounding receiver 120. In general, the channel sounding waveforms mayhave a variety of characteristics, such as those described above, thatmay be specified by the channel sounding transmitter 125 (and/or by anoperator thereof).

In one example, the channel sounding receiver 120 may be used to receivechannel sounding waveforms that are transmitted in an environment fromthe channel sounding transmitter 125, where the channel soundingwaveforms, as received, may be used to calculate or determine themeasures of various wireless channel parameters such as: a compleximpulse response, a path loss, an RSS, a CIR, an excess delay, an RMSdelay spread, an angular spread, a Doppler spread, a fade rate, an AoA,and so forth. For illustrative purposes, the “wireless channel(s)” forwhich the channel sounding receiver 120 is obtaining channel soundingwaveforms and measuring wireless channel parameters may be indicated byreference numeral 190 in FIG. 1.

In one example, the channel sounding receiver 120 includes a pluralityof phased array antennas that may be activated and deactivated accordingto a schedule or otherwise synchronized to the transmission of channelsounding waveforms. In one example, each phased array antenna may bepaired with an RF front end to receive radio frequency (RF) signals fromthe respective phased array antenna and convert the signals intobaseband signals. A digital sampling unit (e.g., an analog-to-digitalconverter (ADC) of a baseband processing unit) may convert the basebandsignals into digital representations of the channel sounding waveformsthat are received via the respective phased array antennas. Forinstance, the digital sampling units may oversample the analog basebandsignals at a sampling interval under the control of timing signals froma clock circuit to create the digital representations of the channelsounding waveforms. In one example, each phased array may cover 90-120degrees in azimuth, 90-180 degrees in elevation, etc., and the phasedarrays may collectively cover 360 degrees in azimuth and 180 degrees inelevation (or greater, e.g., to account for angles below horizon).

In one example, the baseband processing units may output the digitalrepresentations of the channel sounding waveforms to a processor unitthat is configured to perform various operations for determiningmeasures of wireless channel parameters, as described herein. Forinstance, the channel sounding receiver 120 may calculate, based uponthe digital representations of the channel sounding waveforms, a phasedifference between channel sounding waveforms received via respectiveantennas. The processor unit may further determine an angle of arrival(AoA) based upon the antenna positions and the phase difference.

In one example, the channel sounding receiver 120 may receive areference copy or copies of the channel sounding waveforms(s) and/or aset of parameters characterizing the channel sounding waveforms, fromthe channel sounding transmitter 125. Accordingly, the channel soundingreceiver 120 may determine a carrier-to-interference ratio (CIR) bycomparing a sequence received via one of the phased array antennas witha reference copy. Similarly, the channel sounding receiver 120 maycalculate a complex impulse response, a path loss, an RSS, a CIR, anexcess delay, an RMS delay spread, an angular spread, a Doppler spread,a fade rate, an AoA, or the like, from the digital representations ofthe channel sounding waveforms.

As described above, the channel sounding transmitter 125 and the channelsounding receiver 120 may establish a wireless side link for exchangingtiming information (broadly, a synchronization signal) as well as forconveying information regarding the channel sounding waveform (e.g., areference copy and/or modulation parameters, beam information, etc.). Toillustrate, a wireless side link may include a communication session viacellular network infrastructure, e.g., including at least wireless links192 and 193. Alternatively, the wireless side link may comprise awireless communication session via a non-cellular wireless networkingprotocol, such as IEEE 802.11/Wi-Fi, or the like, or via a wirelesscommunication session in accordance with a set of non-restrictedfrequency resources (e.g., using ISM band frequencies). In suchexamples, the non-cellular wireless communication session may include anaccess point (AP) coordinator (not shown) and/or a peer-to-peer session(represented by wireless link 191 in FIG. 1). In addition, in suchexamples, the non-cellular wireless link(s) may comprise out-of-bandwireless links (which use different frequencies from the channelsounding waveforms and the “wireless channel(s)” 190. In examples wherethe wireless side link comprises an out-of-band wireless link, thechannel sounding receiver 120 and the channel sounding transmitter 125may use a different set of antennas, RF front ends, and/or basebandunits than those which are used for channel sounding/channel propertymeasurements in accordance with the present disclosure.

In still another example, wireless link 190 may represent an in-bandwireless link, which may share the same frequency resources as thechannel sounding waveforms and/or the “wireless channel(s)” 190, butwhich may utilize different time resources (different time blocks). Forinstance, the channel sounding waveforms may be for millimeter wavefrequencies (30 GHz to 300 GHz) as carrier frequencies, where thewireless side link utilizes the same set of frequencies or frequencybands.

The wireless side link may be used to transmit a synchronization signalby the channel sounding transmitter 125, in addition to otherinformation regarding one or more channel sounding waveforms, such asreference copies or parameters thereof, beam information, timinginformation, etc. The wireless side link may also be used by the channelsounding receiver 120 to notify the channel sounding transmitter 125that the channel sounding receiver 120 is in position and ready tomeasure, to confirm that a clock circuit of the channel soundingreceiver 120 is matched to the synchronization signal, to confirmsuccessful measurements to the channel sounding transmitter 125 or toindicate one or more failed measurements, to report the measurements tothe channel sounding transmitter 125, and so forth.

In one example, the channel sounding receiver 120 and channel soundingtransmitter 125 may each comprise all or a portion of a computing deviceor system, such as computing system 500, and/or processing system 502 asdescribed in connection with FIG. 5 below, and may be configured toprovide one or more functions for synchronizing a mobile channelsounding transmitter and a channel sounding receiver via a wireless sidelink, and for performing various other operations in accordance with thepresent disclosure. For instance, channel sounding transmitter 125 maybe configured to perform functions such as those described below inconnection with the example method 300 of FIG. 3. Similarly, channelsounding receiver 120 may be configured to perform functions such asthose described below in connection with the example method 400 of FIG.4.

In addition, it should be noted that as used herein, the terms“configure,” and “reconfigure” may refer to programming or loading aprocessing system with computer-readable/computer-executableinstructions, code, and/or programs, e.g., in a distributed ornon-distributed memory, which when executed by a processor, orprocessors, of the processing system within a same device or withindistributed devices, may cause the processing system to perform variousfunctions. Such terms may also encompass providing variables, datavalues, tables, objects, or other data structures or the like which maycause a processing system executing computer-readable instructions,code, and/or programs to function differently depending upon the valuesof the variables or other data structures that are provided. As referredto herein a “processing system” may comprise a computing deviceincluding one or more processors, or cores (e.g., as illustrated in FIG.5 and discussed below) or multiple computing devices collectivelyconfigured to perform various steps, functions, and/or operations inaccordance with the present disclosure.

In one example, the EPC network 105 provides various functions thatsupport wireless services in the LTE environment. In one example, EPCnetwork 105 is an Internet Protocol (IP) packet core network thatsupports both real-time and non-real-time service delivery across a LTEnetwork, e.g., as specified by the 3GPP standards. In one example, cellsites 111 and 112 in the access network 103 are in communication withthe EPC network 105 via baseband units in BBU pool 114. In operation, UE116 may access wireless services via the cell site 111 and UE 117 mayaccess wireless services via the cell site 112 located in the accessnetwork 103. It should be noted that any number of cell sites can bedeployed in access network. In one illustrative example, the accessnetwork 103 may comprise one or more cell sites.

In EPC network 105, network devices such as Mobility Management Entity(MME) 107 and Serving Gateway (SGW) 108 support various functions aspart of the cellular network 101. For example, MME 107 is the controlnode for the LTE access network. In one embodiment, MME 107 isresponsible for UE (User Equipment) tracking and paging (e.g., such asretransmissions), bearer activation and deactivation process, selectionof the SGW, and authentication of a user. In one embodiment, SGW 108routes and forwards user data packets, while also acting as the mobilityanchor for the user plane during inter-cell handovers and as the anchorfor mobility between 5G, LTE and other wireless technologies, such as 2Gand 3G wireless networks.

In addition, EPC network 105 may comprise a Home Subscriber Server (HSS)109 that contains subscription-related information (e.g., subscriberprofiles), performs authentication and authorization of a wirelessservice user, and provides information about the subscriber's location.The EPC network 105 may also comprise a packet data network (PDN)gateway 110 which serves as a gateway that provides access between theEPC network 105 and various data networks, e.g., service network 140,IMS core network 115, other network(s) 180, and the like. The packetdata network gateway 110 is also referred to as a PDN gateway, a PDN GWor a PGW. In addition, the EPC network 105 may include a Diameterrouting agent (DRA) 106, which may be engaged in the proper routing ofmessages between other elements within EPC network 105, and with othercomponents of the system 100, such as a call session control function(CSCF) (not shown) in IMS core network 115. For clarity, the connectionsbetween DRA 106 and other components of EPC network 105 are omitted fromthe illustration of FIG. 1.

In one example, service network 140 may comprise one or more devices,such as application server (AS) 145 for providing services tosubscribers, customers, and or users. For example, telecommunicationservice provider network 170 may provide a cloud storage service, webserver hosting, and other services. As such, service network 140 mayrepresent aspects of telecommunication service provider network 170where infrastructure for supporting such services may be deployed. Inone example, AS 145 may comprise all or a portion of a computing deviceor system, such as computing system 500, and/or processing system 502 asdescribed in connection with FIG. 5 below, specifically configured toprovide one or more service functions in accordance with the presentdisclosure, such as a network-based secure data storage for wirelesschannel parameter measurement records. For instance, channel soundingreceiver 120 and/or channel sounding transmitter 125 may forwardmeasurements of wireless channel parameters from channel soundingreceiver 120 to AS 145 for storage. Either or both of channel soundingreceiver 120 and channel sounding transmitter 125 may also forwardadditional data to AS 145 for storage, such as reference copies of thechannel sounding waveform(s) and/or parameters thereof, transmit beaminformation, time stamp information, location information of the channelsounding receiver 120 and channel sounding transmitter 125, and soforth. Although a single application server, AS 145, is illustrated inservice network 140, it should be understood that service network 140may include any number of components to support one or more servicesthat may be provided to one or more subscribers, customers, or users bythe telecommunication service provider network 170.

In one example, other networks 180 may represent one or more enterprisenetworks, a circuit switched network (e.g., a public switched telephonenetwork (PSTN)), a cable network, a digital subscriber line (DSL)network, a metropolitan area network (MAN), an Internet service provider(ISP) network, and the like. In one example, the other networks 180 mayinclude different types of networks. In another example, the othernetworks 180 may be the same type of network. In one example, the othernetworks 180 may represent the Internet in general.

In accordance with the present disclosure, any one or more of thecomponents of EPC network 105 may comprise network functionvirtualization infrastructure (NFVI), e.g., SDN host devices (i.e.,physical devices) configured to operate as various virtual networkfunctions (VNFs), such as a virtual MME (vMME), a virtual HHS (vHSS), avirtual serving gateway (vSGW), a virtual packet data network gateway(vPGW), and so forth. For instance, MME 107 may comprise a vMME, SGW 108may comprise a vSGW, and so forth. In this regard, the EPC network 105may be expanded (or contracted) to include more or less components thanthe state of EPC network 105 that is illustrated in FIG. 1. In thisregard, the EPC network 105 may also include a self-optimizing network(SON)/software defined network (SDN) controller 102.

In one example, SON/SDN controller 102 may function as a self-optimizingnetwork (SON) orchestrator that is responsible for activating anddeactivating, allocating and deallocating, and otherwise managing avariety of network components. In one example, SON/SDN controller 102may further comprise a SDN controller that is responsible forinstantiating, configuring, managing, and releasing VNFs. For example,in a SDN architecture, a SDN controller may instantiate VNFs on sharedhardware, e.g., NFVI/host devices/SDN nodes, which may be physicallylocated in various places.

The foregoing description of the system 100 is provided as anillustrative example only. In other words, the example of system 100 ismerely illustrative of one network configuration that is suitable forimplementing embodiments of the present disclosure. As such, otherlogical and/or physical arrangements for the system 100 may beimplemented in accordance with the present disclosure. For example,channel sounding may utilize multiple channel sounding receivers toreceive channel sounding signals/waveforms from channel soundingtransmitter 125. Similarly, multiple mobile channel soundingtransmitters may be utilized for channel sounding in conjunction withchannel sounding receiver 120 and/or multiple channel soundingreceivers.

In one example, the system 100 may be expanded to include additionalnetworks, such as network operations center (NOC) networks, additionalaccess networks, and so forth. The system 100 may also be expanded toinclude additional network elements such as border elements, routers,switches, policy servers, security devices, gateways, a contentdistribution network (CDN) and the like, without altering the scope ofthe present disclosure. In addition, system 100 may be altered to omitvarious elements, substitute elements for devices that perform the sameor similar functions, combine elements that are illustrated as separatedevices, and/or implement network elements as functions that are spreadacross several devices that operate collectively as the respectivenetwork elements. For instance, in one example, SON/SDN controller 102may be spilt into separate components to operate as a SON orchestratorand a SDN controller, respectively. Similarly, although the SON/SDNcontroller 102 is illustrated as a component of EPC network 105, inanother example SON/SDN controller 102, and/or other network componentsmay be deployed in an IMS core network 115 instead of being deployedwithin the EPC network 105, or in other portions of system 100 that arenot shown, while providing essentially the same functionality.

In addition, although aspects of the present disclosure have beendiscussed above in the context of a long term evolution (LTE)-based corenetwork (e.g., EPC network 105), examples of the present disclosure arenot so limited. For example, as illustrated in FIG. 1, the cellularnetwork 101 may represent a “non-stand alone” (NSA) mode architecturewhere 5G radio access network components, such as a “new radio” (NR),“gNodeB” (or “gNB”), and so forth are supported by a 4G/LTE core network(e.g., a Evolved Packet Core (EPC) network 105). However, in anotherexample, system 100 may instead comprise a 5G “standalone” (SA) modepoint-to-point or service-based architecture where components andfunctions of EPC network 105 are replaced by a 5G core network, whichmay include an access and mobility management function (AMF), a userplane function (UPF), a session management function (SMF), a policycontrol function (PCF), a unified data management function (UDM), anauthentication server function (AUSF), an application function (AF), anetwork repository function (NRF), and so on. For instance, in such anetwork, application server (AS) 145 of FIG. 1 may represent anapplication function (AF) for adjusting aspects of a cellular network inresponse to measurements of wireless channel parameters by a receiverdevice, and for performing various other operations in accordance withthe present disclosure. In addition, any one or more of cell sites111-113 may comprise 2G, 3G, 4G and/or LTE radios, e.g., in addition to5G new radio (NR) functionality. For instance, in non-standalone (NSA)mode architecture, LTE radio equipment may continue to be used for cellsignaling and management communications, while user data may rely upon a5G new radio (NR), including millimeter wave communications, forexample. Thus, these and other modifications are all contemplated withinthe scope of the present disclosure.

FIG. 2 illustrates examples of synchronizing a mobile channel soundingtransmitter and a channel sounding receiver via a wireless side link. Ina first example, a channel sounding system 210 includes a channelsounding transmitter 211 (e.g., a mobile channel sounding transmitter)and a channel sounding receiver 214. The channel sounding transmitter211 transmits a sounding signal 217 (e.g., a channel sounding signal, orchannel sounding waveform) via transmitter 212 which may be received bychannel sounding receiver 214 via receiver 215. The transmitter 212 maycomprise components for radio transmission in a frequency band ofinterest, such as a digital baseband unit, a digital to analogconversion unit, a baseband to RF upconversion unit, one or moreantennas and/or antenna arrays, and so forth. Similarly, the receiver215 may comprise one or more antennas and/or antenna arrays, an RF tobaseband conversion unit, an analog to digital conversion unit, adigital baseband unit, and so forth. In one example, the transmitter 212and receiver 215 may comprise transceivers equipped for bothtransmission and reception of RF signals. For instance, transmitter 212and receiver 215 may include upconversion/downconversion units,analog-to-digital and digital-to-analog conversion units, and so forth.

The channel sounding transmitter 211 and channel sounding receiver 214may establish a wireless side link which may be used to conveysynchronization signal 218 (in addition to additional informationregarding one or more channel sounding waveforms and/or othercommunications to coordinate between the channel sounding transmitter211 and the channel sounding receiver 214). In the present example, thewireless side link may comprise a cellular or non-cellular communicationsession between wireless modules 213 and 216. For instance, wirelessmodules 213 and 216 may comprise IEEE 802.11/Wi-Fi transceivers toestablish a Wi-Fi communication session, or may comprise cellulartransceivers (e.g., LTE transceivers) to establish a cellularcommunication session. In such an example, the wireless side link forconveying the synchronization signal 218 (and in some cases, additionalinformation regarding the channel sounding signal 217 and/or othercommunications) may include or may traverse cellular networkinfrastructure, such as a base station, a serving gateway, etc., orequipment providing an IEEE 802.11 network, such as a wireless router oraccess point (AP).

In a second example, a channel sounding system 220 includes a channelsounding transmitter 221 (e.g., a mobile channel sounding transmitter)and a channel sounding receiver 224. The channel sounding transmitter221 transmits a sounding signal 227 (e.g., a channel sounding signal, orchannel sounding waveform) via transmitter 222 which may be received bychannel sounding receiver 224 via receiver 225. The transmitter 222 andthe receiver 225 may comprise the same or similar components astransmitter 212 and receiver 215 of the channel sounding system 210. Inaddition, the channel sounding transmitter 221 and channel soundingreceiver 224 may establish a wireless side link which may be used toconvey synchronization signal 228 (in addition to additional informationregarding one or more channel sounding waveforms and/or othercommunications to coordinate between the channel sounding transmitter221 and the channel sounding receiver 224). In the present example, thewireless side link may comprise a communication session between themobile channel sounding transmitter and the channel sounding receiver inaccordance with a set of non-restricted frequency resources (e.g., usingone or more ISM bands). For instance, channel sounding transmitter 221and channel sounding receiver 224 may comprise software defined radio(SDR) modules 223 and 226, respectively, to establish the communicationsession. Similar to the channel sounding system 210, the channelsounding signal 227 utilizes a different set of time and frequencyresources than the synchronization signal 228.

In a third example, a channel sounding system 230 includes a channelsounding transmitter 231 (e.g., a mobile channel sounding transmitter)and a channel sounding receiver 234. The channel sounding transmitter231 transmits a sounding signal 237 (e.g., a channel sounding signal, orchannel sounding waveform) via transceiver 232. The transceiver 232 maycomprise the same or similar components as transmitters 212 and 222 ofchannel sounding systems 210 and 220, respectively. The sounding signal237 may be received by channel sounding receiver 234 via transceiver235, which may comprise the same or similar components as receivers 215and 225 of channel sounding systems 210 and 220, respectively. Inaddition, the channel sounding transmitter 231 and channel soundingreceiver 234 may establish an out-of-band wireless link via transceivers232 and 235 using frequency resources that are within an operationalbandwidth of the transceivers 232 and 235 that are used for channelsounding, but outside of the frequencies within the operationalbandwidth that are used for the channel sounding signal 237. Forinstance, the graph 239 illustrates one example of the sounding signal237 and synchronization signal 238 with the channel sounding bandwidth(e.g., the operational range of the transceivers 232 and 235 and/or theoperational range of the transceivers 232 and 235 subject to anyconstraints such as permitted use of certain frequencies or frequencybands within the geographic region where the channel sounding system 230is used).

In a fourth example, a channel sounding system 240 includes a channelsounding transmitter 241 (e.g., a mobile channel sounding transmitter)and a channel sounding receiver 244. The channel sounding transmitter241 transmits a sounding signal 247 (e.g., a channel sounding signal, orchannel sounding waveform) via transceiver 242. The transceiver 242 maycomprise the same or similar components as transmitters 212, 222, and/ortransceiver 232 of channel sounding systems 210, 220, and 230,respectively. The sounding signal 247 may be received by channelsounding receiver 244 via transceiver 245, which may comprise the sameor similar components as receivers 215, 225, and/or transceiver 235 ofchannel sounding systems 210, 220 and 230, respectively. In addition,the channel sounding transmitter 231 and channel sounding receiver 234may establish an in-band wireless link via transceivers 242 and 245which uses the same frequency resources as are used for the channelsounding signal 247 but which utilizes different, non-overlapping timeslots from the channel sounding signal 247. For instance, the graph 249illustrates one example of the sounding signal 247 and synchronizationsignal 248 with a time/frequency grid which may be utilized by thechannel sounding system 240.

It should be noted that although the channel sounding signals 217, 227,237, and 247 and the synchronization signals 218, 228, 238, and 248 arereferred to in the singular form, it should be understood that therespective systems 210, 220, 230, and 240 may utilize a plurality ofchannel sounding signals and/or a plurality of synchronization signals,which may be of the same form, or which may have different forms.Similarly, the graphs 239 and 249 may have different forms, such assynchronization signal 238 utilizing lower frequencies and the soundingsignal 237 utilizing higher frequencies within the channel soundingbandwidth and/or operational range of the transceivers 232 and 235,additional channel sounding signal(s) 248 between successivesynchronization signal(s) 247, and so forth. In addition, it should beunderstood that any of the channel sounding receivers 214, 224, 234, and244 may similarly comprise mobile channel sounding receivers that may beportable and which may be moved from location to location with relativeease. Thus, these and other modifications are all contemplated withinthe scope of the present disclosure.

FIG. 3 illustrates a flowchart of an example method 300 forsynchronizing a mobile channel sounding transmitter and a channelsounding receiver via a wireless side link, in accordance with thepresent disclosure. In one example, steps, functions and/or operationsof the method 300 may be performed by a device as illustrated in FIG. 1,e.g., a channel sounding transmitter, or any one or more componentsthereof, such as a processing system, one or more transceivers, one ormore antennas or antenna arrays (e.g., a phased array antenna), and soforth. In accordance with the present disclosure a processing system mayinclude one or more processors, which can include CPUs, PLDs, or acombination thereof. For instance, a processing system may includecentral processing unit, a digital baseband unit, and so forth. In oneexample, the steps, functions, or operations of method 300 may beperformed by a computing device or system 500, and/or a processingsystem 502 as described in connection with FIG. 5 below. For instance,the computing device 500 may represent at least a portion of a mobilechannel sounding transmitter in accordance with the present disclosure.For illustrative purposes, the method 300 is described in greater detailbelow in connection with an example performed by a processing system.The method 300 begins in step 305 and may proceed to optional step 310or to step 320.

At optional step 310, the processing system (e.g., of a mobile channelsounding transmitter) may obtain a notification of a channel soundingreceiver that is ready to measure one or more wireless channelparameters via one or more channel sounding waveforms. The notificationmay comprise a manual input from an operator, such as pressing a button,entering a command via a graphical user interface or command line, andso forth, or may comprise a wireless communication from a channelsounding receiver. For instance, the channel sounding receiver mayutilize an in-band or out-of-band signal to indicate the presence of thechannel sounding receiver and an intention to establish a wireless sidelink. In one example, the notification may include estimated or generallocation information of the channel sounding receiver such that theprocessing system may determine the general direction of the channelsounding receiver in relation of the mobile channel soundingtransmitter, e.g., within a 60-90 degree range within a 120 degreerange, etc.

At step 320, the processing system establishes a wireless side linkbetween the mobile channel sounding transmitter and the channel soundingreceiver. For example, the wireless side link may comprise anout-of-band wireless link, which may include a communication sessionbetween the mobile channel sounding transmitter and the channel soundingreceiver via a cellular network. In such an example, at least onechannel sounding waveform is transmitted (e.g., at step 350) via a firstset of time and frequency resources that is different from a second setof time and frequency resources that is utilized by the cellularnetwork.

In one example, the out-of-band wireless link may comprise acommunication session between the mobile channel sounding transmitterand the channel sounding receiver in accordance with a non-cellularwireless networking protocol, such as a wireless local area networkprotocol (e.g., IEEE 802.11, or the like), or a wireless peer-to-peerprotocol (e.g., IEEE 802.15, Bluetooth, ZigBee, etc.). In such anexample, the at least one channel sounding waveform is transmitted(e.g., at step 350) via a set of frequency resources that is differentfrom a set of frequency resources that is utilized by the non-cellularwireless networking protocol.

In one example, the out-of-band wireless link comprises a communicationsession between the mobile channel sounding transmitter and the channelsounding receiver in accordance with a set of non-restricted frequencyresources. For instance, the set of non-restricted frequency resourcesmay comprise at least a portion of an industrial, scientific, andmedical (ISM) radio band. In such an example, the at least one channelsounding waveform is transmitted (e.g., at step 350) via a set offrequency resources that is different from the set of non-restrictedfrequency resources. In all of the foregoing examples, at least onechannel sounding waveform may be transmitted (e.g., at step 350) via afirst transceiver of the mobile channel sounding transmitter, and thewireless side link may be established via a second transceiver of themobile channel sounding transmitter that is different from the firsttransceiver. In addition, the channel sounding receiver may also usedifferent receivers (e.g., different transceivers) for wireless sidelink and channel sounding waveform(s).

In one example, the out-of-band wireless link comprises a communicationsession between the mobile channel sounding transmitter and the channelsounding receiver in accordance with first set of frequency resources,where at least one channel sounding waveform is transmitted (e.g., atstep 350 discussed below) via a second set of frequency resources thatis different from the first set of frequency resources, and where boththe first set of frequency resources and the second set of frequencyresources are within an operational bandwidth of a transceiver of themobile channel sounding transmitter. For instance, the at least onechannel sounding waveform is transmitted via the transceiver (e.g., atstep 350), and the wireless side link is also established via thetransceiver (e.g., at step 320). Similarly, both the first set offrequency resources and the second set of frequency resources may bewithin an operational bandwidth of a receiver/transceiver of the channelsounding receiver.

In another example, the wireless side link comprises an in-band wirelesslink, where the in-band wireless link comprises a communication sessionvia a first set of time and frequency resources, where the first set oftime and frequency resources comprises a first set of frequencies and afirst set of time slots, and where the at least one channel soundingwaveform is transmitted (e.g., at step 350) via a second set of time andfrequency resources, where the second set of time and frequencyresources comprises the first set of frequencies and a second set oftime slots, and where the time slots of the second set of time slots arenon-overlapping with the time slots of the first set of time slots.

At step 330, the processing system transmits, to the channel soundingreceiver, a wireless synchronization signal via the wireless side link.For example, as discussed above, the synchronization signal may conveyclock timing information of the mobile channel sounding transmitter. Inone example, the synchronization signal further conveys informationregarding the at least one channel sounding waveform (to be transmittedat step 350), such as a transmit beam identifier, at least onemodulation parameter of the channel sounding waveform, or timinginformation of the at least one channel sounding waveform. The timinginformation may be relative timing information of the at least onechannel sounding waveform with respect to the synchronization signal, orcan be “absolute” where the absolute time is determinable by the channelsounding receiver by first synching to the synchronization signal. Theinformation regarding the at least one channel sounding waveform mayfurther include an angle of departure (AoD) and/or may include the shapeof the waveform, e.g., return-to-zero (RZ), non-return-to-zero (NRZ), afrequency or range of frequencies, the duration of the waveform, etc. Inan example where the wireless side link comprises an out-of-bandwireless link, the additional information may be obtained via one ormore packets via the out-of-band wireless link.

At optional step 340, the processing system may receive, from thechannel sounding receiver via the wireless side link, a confirmationthat the channel sounding receiver is synchronized to the mobile channelsounding transmitter (in other words, that the channel sounding receiveris synchronized to the wireless synchronization signal). In one example,the confirmation may be understood between the channel sounding receiverand the processing system (of the mobile channel sounding transmitter)to be valid for a certain duration of time, after which aresynchronization may be performed before further channel sounding mayoccur.

At step 350, the processing system transmits the at least one channelsounding waveform, e.g., via one or more antennas of the mobile channelsounding transmitter. In one example, the channel sounding waveforms aretransmitted via at least one directional antenna, e.g., a phased arrayantenna for beamforming. Thus, each of the channel sounding waveformsmay be associated with a particular transmit beam or transmit beamdirection (in azimuth and elevation). The at least one channel soundingwaveform may be transmitted in accordance with any of the time and/orfrequency resources as described above and may have any of theadditional properties as described above and which may be conveyed tothe channel sounding receiver via the wireless side link and/or embeddedin the wireless synchronization signal as described above.

At optional step 360, the processing system may obtain, from the channelsounding receiver, a confirmation of a completion of channel soundingmeasurements in accordance with the at least one channel soundingwaveform. In one example, optional step 360 may include obtaining thewireless channel properties/measurements from the channel soundingreceiver (e.g., via the wireless side link). For instance, the mobilechannel sounding transmitter may aggregate measurements from the channelsounding receiver at a plurality of different locations and/ororientation for combining measurements, for generating coverage maps,for storage and uploading to another device for analysis, and so forth.

At optional step 370, the processing system may determine whether tocontinue. For instance, if there are more measurements to be made withthe channel sounding receiver at the same location and/or orientation,or at a different location and/or orientation, or if there are moremeasurements to be made with the mobile channel sounding transmitter ata different location and/or orientation, and/or with a different angleof departure, with different channel sounding waveform(s), etc., thenthe method may return to step 310 or to step 330. To illustrate, themobile channel sounding transmitter may be moved to a different locationand/or orientation and may again identify a channel sounding receiverready to perform channel sounding measurements, may establish a wirelessside link (or reestablish a wireless side link, if the wireless sidelink was lost or released after the first iteration of the method 300),may transmit a synchronization signal, may receive confirmation that thechannel sounding receiver is synchronized, may transmit one or morechannel sounding waveforms, and so forth. Otherwise, the method 300 mayproceed to step 395 where the method ends.

It should be noted that the method 300 may be expanded to includeadditional steps, or may be modified to replace steps with differentsteps, to combine steps, to omit steps, to perform steps in a differentorder, and so forth.

For example, the method 300 is described in connection with a singlechannel sounding receiver. However, in another example, multiple channelsounding receivers may establish wireless side links with the processingsystem (of the mobile channel sounding transmitter) and engage inchannel sounding (measuring properties of the wireless channel inaccordance with the channel sounding waveform(s)) simultaneously and/orin a sequence while deployed at different locations in an environment ofinterest. In another example, the method 300 may involve returning tosteps 330 and/or 340 to resynchronize, e.g., if more than a certainperiod of time has passed after which the synchronization of the channelsounding receiver with the mobile channel sounding transmitter is nolonger guaranteed. Thus, these and other modifications are allcontemplated within the scope of the present disclosure.

FIG. 4 illustrates a flowchart of an additional example method 400 forsynchronizing a mobile channel sounding transmitter and a channelsounding receiver via a wireless side link, in accordance with thepresent disclosure. In one example, steps, functions and/or operationsof the method 400 may be performed by a device as illustrated in FIG. 1,e.g., a channel sounding receiver, or any one or more componentsthereof, such as a processing system, one or more transceivers, one ormore antennas or antenna arrays (e.g., a phased array antenna), a GPSunit, and so forth. In accordance with the present disclosure aprocessing system may include one or more processors, which can includeCPUs, PLDs, or a combination thereof. For instance, a processing systemmay include central processing unit, a digital baseband unit, and soforth. In one example, the steps, functions, or operations of method 400may be performed by a computing device or system 500, and/or aprocessing system 502 as described in connection with FIG. 5 below. Forinstance, the computing device 500 may represent at least a portion of achannel sounding receiver in accordance with the present disclosure. Forillustrative purposes, the method 400 is described in greater detailbelow in connection with an example performed by a processing system.The method 400 begins in step 405 and may proceed to optional step 410or to step 420.

At optional step 410, the processing system (e.g., of a channel soundingreceiver) may transmit a notification to a mobile channel soundingtransmitter that the channel sounding receiver is ready to measurewireless channel parameters via one or more channel sounding waveforms.In one example, optional step 410 may comprise receiver-sidecomplementary operations to those described above in connection withoptional step 310 of the method 300.

At step 420, the processing system establishes a wireless side linkbetween the mobile channel sounding transmitter and the channel soundingreceiver. For instance, the wireless side link may comprise anout-of-band wireless link as described above, such as a communicationsession via a cellular network, a communication session in accordancewith a non-cellular wireless networking protocol, or a communicationsession in accordance with a set of non-restricted frequency resources,or may comprise an out-of-band signal that is within a operationalbandwidth of a transceiver that is used for channel sounding but whichutilizes frequency resources that are not used for channel sounding. Inanother example, the wireless side link may comprise an in-band wirelesslink, but may utilize different time and frequency resources than thosethat are used for channel sounding. In one example, step 420 maycomprise receiver-side complementary operations to those described abovein connection with step 320 of the method 300.

At step 430, the processing system obtains a wireless synchronizationsignal from the mobile channel sounding transmitter via the wirelessside link. As described above, in one example, the synchronizationsignal may be modulated to include additional information regarding theat least one channel sounding waveform. In an example where the wirelessside link comprises an out-of-band wireless link, the additionalinformation may be obtained via one or more packets via the out-of-bandwireless link. In one example, optional step 430 may comprisereceiver-side complementary operations to those described above inconnection with step 330 of the method 300.

At optional step 440, the processing system may transmit a notificationto the mobile channel sounding transmitter that the processing system(of the channel sounding receiver) is synchronized to the mobile channelsounding transmitter (in other words, that the channel sounding receiveris synchronized to the wireless synchronization signal). In one example,the confirmation may be understood between the mobile channel soundingtransmitter and the processing system (of the channel sounding receiver)to be valid for a certain duration of time, after which aresynchronization may be performed before further channel sounding mayoccur.

At step 450, the processing system obtains at least one channel soundingwaveform from the mobile channel sounding transmitter. For instance, theprocessing system may receive the at least one channel sounding waveformvia one or more antennas, or antenna arrays (e.g., one or more phasedarrays). The at least one channel sounding waveform may be transmittedin accordance with any of the time and/or frequency resources asdescribed above and may have any of the additional properties asdescribed above and which may be obtained by the processing system fromthe mobile channel sounding transmitter via the wireless side linkand/or embedded in the wireless synchronization signal as describedabove.

In one example, step 450 may include performing at least one measurementof at least one parameter of the wireless channel in accordance with theat least one channel sounding waveform. For instance, the at onewireless channel parameter may comprise one or more of: a compleximpulse response, a path loss, a RSS, an excess delay, an RMS delayspread, an angular spread, a Doppler spread, a fade rate, an angle ofarrival (AoA), and so forth. In one example, the processing system maytag and/or store measurements with additional data, such as a locationof the channel sounding receiver, an orientation of the channel soundingreceiver, a timestamp, and so forth.

At optional step 460, the processing system may transmit a confirmationof a completion of channel sounding measurements in accordance with theat least one channel sounding waveform (e.g., via the wireless sidelink). In one example, optional step 460 may include transmitting thewireless channel properties/measurements to the mobile channel soundingtransmitter. For instance, the mobile channel sounding transmitter mayaggregate measurements from the channel sounding receiver at a pluralityof different locations and/or orientation for combining measurements,for generating coverage maps, for storage and uploading to anotherdevice for analysis, and so forth.

At optional step 470, the processing system may determine whether tocontinue. For instance, if there are more measurements to be made withthe channel sounding receiver at the same location and/or orientation,or at a different location and/or orientation, or if there are moremeasurements to be made with the mobile channel sounding transmitter ata different location and/or orientation, and/or with a different angleof departure, with different channel sounding waveform(s), etc., thenthe method may return to step 410 or to step 430. To illustrate, thechannel sounding receiver may be moved to a different location and/ororientation and may again notify a mobile channel sounding transmitterthat the channel sounding receiver is ready to perform channel soundingmeasurements, may establish a wireless side link (or reestablish awireless side link, if the wireless side link was lost or released afterthe first iteration of the method 400), may receive a synchronizationsignal, may transmit confirmation that the channel sounding receiver issynchronized, may receive one or more channel sounding waveforms, and soforth. Otherwise, the method 400 may proceed to step 495 where themethod ends.

It should be noted that the method 400 may be expanded to includeadditional steps, or may be modified to replace steps with differentsteps, to combine steps, to omit steps, to perform steps in a differentorder, and so forth. For example, the method 400 is described inconnection with a single mobile channel sounding transmitter. However,in another example, multiple mobile channel sounding transmitters mayestablish wireless side links with the processing system (of the channelsounding receiver) and engage in transmitting channel soundingwaveform(s) while deployed at different locations in an environment ofinterest. In another example, the method 400 may involve returning tosteps 430 and/or 440 to resynchronize, e.g., if more than a certainperiod of time has passed after which the synchronization of the channelsounding receiver with the mobile channel sounding transmitter is nolonger guaranteed. Thus, these and other modifications are allcontemplated within the scope of the present disclosure.

In addition, although not specifically specified, one or more steps,functions, or operations of the method 300 or the method 400 may includea storing, displaying, and/or outputting step as required for aparticular application. In other words, any data, records, fields,and/or intermediate results discussed in the method(s) can be stored,displayed, and/or outputted either on the device executing the method(s)or to another device, as required for a particular application.Furthermore, steps, blocks, functions or operations in FIG. 3 or FIG. 4that recite a determining operation or involve a decision do notnecessarily require that both branches of the determining operation bepracticed. In other words, one of the branches of the determiningoperation can be deemed as an optional step. Furthermore, steps, blocks,functions or operations of the above described method(s) can becombined, separated, and/or performed in a different order from thatdescribed above, without departing from the example examples of thepresent disclosure.

FIG. 5 depicts a high-level block diagram of a computing device orprocessing system specifically programmed to perform the functionsdescribed herein. As depicted in FIG. 5, the processing system 500comprises one or more hardware processor elements 502 (e.g., a centralprocessing unit (CPU), a microprocessor, or a multi-core processor), amemory 504 (e.g., random access memory (RAM) and/or read only memory(ROM)), a module 505 for synchronizing a mobile channel soundingtransmitter and a channel sounding receiver via a wireless side link,and various input/output devices 506 (e.g., storage devices, includingbut not limited to, a tape drive, a floppy drive, a hard disk drive or acompact disk drive, a receiver, a transmitter, a speaker, a display, aspeech synthesizer, an output port, an input port and a user inputdevice (such as a keyboard, a keypad, a mouse, a microphone and thelike)). In accordance with the present disclosure input/output devices506 may also include antenna elements, antenna arrays, remote radioheads (RRHs), baseband units (BBUs), transceivers, power units, GPSunits, and so forth. Although only one processor element is shown, itshould be noted that the computing device may employ a plurality ofprocessor elements. Furthermore, although only one computing device isshown in the figure, if the method 300 or the method 400 as discussedabove is implemented in a distributed or parallel manner for aparticular illustrative example, i.e., the steps of the above method 300or method 400, or the entire method 300 or method 400, is implementedacross multiple or parallel computing devices, e.g., a processingsystem, then the computing device of this figure is intended torepresent each of those multiple computing devices.

Furthermore, one or more hardware processors can be utilized insupporting a virtualized or shared computing environment. Thevirtualized computing environment may support one or more virtualmachines representing computers, servers, or other computing devices. Insuch virtualized virtual machines, hardware components such as hardwareprocessors and computer-readable storage devices may be virtualized orlogically represented. The hardware processor 502 can also be configuredor programmed to cause other devices to perform one or more operationsas discussed above. In other words, the hardware processor 502 may servethe function of a central controller directing other devices to performthe one or more operations as discussed above.

It should be noted that the present disclosure can be implemented insoftware and/or in a combination of software and hardware, e.g., usingapplication specific integrated circuits (ASIC), a programmable gatearray (PGA) including a Field PGA, or a state machine deployed on ahardware device, a computing device or any other hardware equivalents,e.g., computer readable instructions pertaining to the method discussedabove can be used to configure a hardware processor to perform thesteps, functions and/or operations of the above disclosed method 300 ormethod 400. In one example, instructions and data for the present moduleor process 505 for synchronizing a mobile channel sounding transmitterand a channel sounding receiver via a wireless side link (e.g., asoftware program comprising computer-executable instructions) can beloaded into memory 504 and executed by hardware processor element 502 toimplement the steps, functions, or operations as discussed above inconnection with the illustrative method 300 or method 400. Furthermore,when a hardware processor executes instructions to perform “operations,”this could include the hardware processor performing the operationsdirectly and/or facilitating, directing, or cooperating with anotherhardware device or component (e.g., a co-processor and the like) toperform the operations.

The processor executing the computer readable or software instructionsrelating to the above described method can be perceived as a programmedprocessor or a specialized processor. As such, the present module 505for synchronizing a mobile channel sounding transmitter and a channelsounding receiver via a wireless side link (including associated datastructures) of the present disclosure can be stored on a tangible orphysical (broadly non-transitory) computer-readable storage device ormedium, e.g., volatile memory, non-volatile memory, ROM memory, RAMmemory, magnetic or optical drive, device or diskette, and the like.Furthermore, a “tangible” computer-readable storage device or mediumcomprises a physical device, a hardware device, or a device that isdiscernible by the touch. More specifically, the computer-readablestorage device may comprise any physical devices that provide theability to store information such as data and/or instructions to beaccessed by a processor or a computing device such as a computer or anapplication server.

While various examples have been described above, it should beunderstood that they have been presented by way of illustration only,and not a limitation. Thus, the breadth and scope of any aspect of thepresent disclosure should not be limited by any of the above-describedexamples, but should be defined only in accordance with the followingclaims and their equivalents.

What is claimed is:
 1. A method comprising: establishing, by aprocessing system of a mobile channel sounding transmitter, a wirelessside link between the mobile channel sounding transmitter and a channelsounding receiver; transmitting, by the processing system to the channelsounding receiver, a wireless synchronization signal via the wirelessside link; and transmitting, by the processing system, at least onechannel sounding waveform in accordance with the wirelesssynchronization signal.
 2. The method of claim 1, wherein the wirelessside link comprises an out-of-band wireless link.
 3. The method of claim2, wherein the out-of-band wireless link comprises a communicationsession between the mobile channel sounding transmitter and the channelsounding receiver via a cellular network.
 4. The method of claim 3,wherein the at least one channel sounding waveform is transmitted via afirst set of time and frequency resources that is different from asecond set of time and frequency resources that is utilized by thecellular network.
 5. The method of claim 2, wherein the out-of-bandwireless link comprises a communication session between the mobilechannel sounding transmitter and the channel sounding receiver inaccordance with a non-cellular wireless networking protocol.
 6. Themethod of claim 5, wherein the non-cellular wireless networking protocolcomprises: a wireless local area network protocol; or a wirelesspeer-to-peer protocol.
 7. The method of claim 5, wherein the at leastone channel sounding waveform is transmitted via a set of frequencyresources that is different from a set of frequency resources that isutilized by the non-cellular wireless networking protocol.
 8. The methodof claim 2, wherein the out-of-band wireless link comprises acommunication session between the mobile channel sounding transmitterand the channel sounding receiver in accordance with a set ofnon-restricted frequency resources.
 9. The method of claim 8, whereinthe set of non-restricted frequency resources comprises at least aportion of an industrial, scientific, and medical radio band.
 10. Themethod of claim 8, wherein the at least one channel sounding waveform istransmitted via a set of frequency resources that is different from theset of non-restricted frequency resources.
 11. The method of claim 2,wherein the at least one channel sounding waveform is transmitted via afirst transceiver of the mobile channel sounding transmitter, andwherein the wireless side link is established via a second transceiverof the mobile channel sounding transmitter that is different from thefirst transceiver.
 12. The method of claim 2, wherein the at least onechannel sounding waveform is transmitted via a transceiver of the mobilechannel sounding transmitter, and wherein the wireless side link isestablished via the transceiver.
 13. The method of claim 12, wherein theout-of-band wireless link comprises a communication session between themobile channel sounding transmitter and the channel sounding receiver inaccordance with a first set of frequency resources, wherein the at leastone channel sounding waveform is transmitted via a second set offrequency resources that is different from the first set of frequencyresources, and wherein both the first set of frequency resources and thesecond set of frequency resources are within an operational bandwidth ofthe transceiver.
 14. The method of claim 1, wherein the wirelesssynchronization signal conveys clock timing information of the mobilechannel sounding transmitter.
 15. The method of claim 14, wherein thewireless synchronization signal further conveys information regardingthe at least one channel sounding waveform.
 16. The method of claim 15,wherein the information regarding the at least one channel soundingwaveform includes a transmit beam identifier.
 17. The method of claim15, wherein the information regarding the at least one channel soundingwaveform includes at least one of: at least one modulation parameter ofthe at least one channel sounding waveform; or timing information of theat least one channel sounding waveform.
 18. The method of claim 15,wherein the wireless synchronization signal is modulated to include theinformation regarding the at least one channel sounding waveform.
 19. Amobile channel sounding transmitter comprising: a processing systemincluding at least one processor; and a computer-readable medium storinginstructions which, when executed by the processing system, cause theprocessing system to perform operations, the operations comprising:establishing a wireless side link between the mobile channel soundingtransmitter and a channel sounding receiver; transmitting, to thechannel sounding receiver, a wireless synchronization signal via thewireless side link; and transmitting at least one channel soundingwaveform in accordance with the wireless synchronization signal.
 20. Anon-transitory computer-readable medium storing instructions which, whenexecuted by a processing system of a mobile channel sounding transmitterincluding at least one processor, cause the processing system to performoperations, the operations comprising: establishing a wireless side linkbetween the mobile channel sounding transmitter and a channel soundingreceiver; transmitting, to the channel sounding receiver, a wirelesssynchronization signal via the wireless side link; and transmitting atleast one channel sounding waveform in accordance with the wirelesssynchronization signal.